MONDAY, Dec. 7, 2015 (HealthDay News) -- Young American gay and bisexual men who have detectable blood levels of HIV -- the virus that causes AIDS -- are also more likely to engage in risky sexual behavior that might spread the virus, a new study has found.

"While many of these young men are engaged in care, and success stories are many, we still have work to do to reduce the rate of new infections," study author Patrick Wilson, an assistant professor of sociomedical sciences at Columbia University's Mailman School of Public Health in New York City, said in a university news release.

Different strategies to help prevent HIV infections and promote safe sex are needed for this group, his team wrote in the Dec. 7 issue of the journal JAMA Pediatrics.

According to the researchers, young men between the ages of 13 and 29 who are gay or bisexual are particularly vulnerable to infection with HIV and now account for more than 25 percent of new infections in the United States each year.

The new study sought to determine who is most at risk, and why. The research involved nearly 1,000 young gay and bisexual men between the ages of 15 and 26. All had visited teen HIV clinics in the United States between December 2009 and June 2012.

According to Wilson's team, more than two-thirds of the men -- 69 percent -- had detectable levels of HIV.

Investigating further, the researchers found that 46 percent of these young men had engaged in anal sex without a condom over the past three months. Moreover, 31 percent of the participants who had a partner with a different HIV status -- one was infected, one was not -- engaged in sexual behavior that put the uninfected partner at risk.

Young men with detectable levels of the virus were more likely to have anal sex without a condom with a partner who didn't have HIV, compared to participants who did not have detectable levels of the virus, the Columbia study showed.

Of those with detectable HIV, 55 percent reported having anal sex without a condom. In contrast, 44 percent of the young gay men whose HIV was suppressed or undetectable (typically due to medication use) did the same.

Among the men with detectable HIV, 35 percent had unprotected anal sex with an HIV-negative partner. Of the men with suppressed HIV, 25 percent had unsafe sex with a partner who had a different HIV status.

Risky sexual behavior was more common among gay and bisexual men with detectable HIV who also had problems with substance abuse, the researchers noted. It was also more common among the men with detectable HIV who disclosed their status to their partners.

"Combination HIV prevention and treatment interventions, which include behavioral, biomedical and structural strategies to increase viral suppression and reduce HIV transmission risk behaviors, that target HIV-infected young men who have sex with men are needed," Wilson said. "To truly curb HIV incidence among this group of individuals, we cannot solely rely on one strategy to prevent and treat HIV."

One expert said young gay men remain a source of concern when it comes to HIV infection.

"We have known that HIV has decreased in most age groups in the United States, but continues to increase in all patients aged 13-24, and even more so in gay and bisexual men in this age group," said Dr. David Rosenthal, who directs the Center for Young Adult, Adolescent, and Pediatric HIV at
North Shore-LIJ Health System in Great Neck, N.Y.

The study suggests that men "who were most likely to have condomless anal intercourse with a person who is not living with HIV were black/African American race, drank alcohol daily and were at-risk teen substance abusers," he said. "Thus, we need to make sure our HIV prevention strategies are specifically reaching out to those individuals."

One proven HIV prevention strategy is the use of drugs like Truvada, or PreP, "an FDA-approved medication that is given daily to patients who do not have HIV, but who are engaging in behaviors which could make them acquire HIV, in order to prevent the transmission of HIV," Rosenthal said.

"This study speaks to specific subpopulations of patients who may most need PrEP, and how we must reach out to these patients -- who traditionally are underserved by the medical community -- to provide them with the best health care we can," he added.